Paralleling transfomers NEC

[ron]

Correct. See this for details:


http://www.facilitiesnet.com/whitepapers/pdfs/schneiderelectric_111711.pdf

Example 2 on page 9 of that pdf - the result surprises me. I would have thought both transformers would have shared the load like in Example 1, which in Example 2 would have overloaded the 1MVA unit.

 

[mbrooke]

Example 2 on page 9 of that pdf - the result surprises me. I would have thought both transformers would have shared the load like in Example 1, which in Example 2 would have overloaded the 1MVA unit.

I dont follow. If both transfomers have the same impedance, a 5 MVA and 1 MVA unit will see 5MVA and 1 MVA when feeding 6MVA of load respectably.

 

[ron]

I dont follow. If both transfomers have the same impedance, a 5 MVA and 1 MVA unit will see 5MVA and 1 MVA when feeding 6MVA of load respectably.

I would have thought each would see 3MVA in your example. Same impedance so same sharing, but clearly I'm missing something.

 

[Smart $]

I don't see that as 'switched as a unit'.

So one switch which when operated energizes or de-energizes both transformers is not "switched as a unit"?

 

[winnie]

Example 2 on page 9 of that pdf - the result surprises me. I would have thought both transformers would have shared the load like in Example 1, which in Example 2 would have overloaded the 1MVA unit.

If the transformers had the same impedance, then you would be correct.

I believe that the transformers have the same % impedance, and thus the smaller transformer actually has a higher impedance.

-Jon